It is known that the bending of an optical fiber, juxtaposed with a light source at one end and confronted by a photodetector at the opposite end, attenuates the luminous radiation transmitted therethrough. It has been found, in fact, that the effect of transverse deformation as a means for varying the transmitted radiation can be optimized by applying pressure to the fiber simultaneously at relatively offset, diametrically opposite points equispaced along its axis by a distance determined by its structural and optical parameters. Reference in this connection may be made to a report based on studies by G. Zeidler, published at the Second European Colloquium on Fiber-Optical Transmission held Sept. 27, 1976 in Paris. That report dealt particularly with periodic curvatures introduced in the fibers by a pair of jaws with relatively staggered teeth offset by half the recurrence period of these deformations. This recurrence period is a function of the wavelength of the transmitted light.
Various assemblies of this nature serving for the measurement of mechanical forces are disclosed in Swedish Pat. No. 410,521. The utilization of deformations of a light-guiding structure in an optical strain gauge is the subject matter of my prior U.S. Pat. No. 4,163,397.
The conventional use of jaws with fixedly spaced teeth as a means for periodically deforming an optical fiber has serious drawbacks. Thus, such a pair of jaws can be applied only to a fiber section of limited length and several jaws of identical structure would have to be provided if two or more such sections were to be deformed simultaneously. Alternatively, as taught in the above-identified Swedish patent, the jaws can be widened to accommodate several turns of a fiber looped therearound. The high precision required in the manufacture of their closely spaced teeth makes these devices in either case rather expensive.